The toxic element ARSENIC is a chemical element with the symbol As and atomic number 33. It is a metalloid that occurs in nature, usually in combination with sulfur and metals, and has various allotropes. ARSENIC is a notorious poison and has been used in many homicides throughout history. It is also used in some industrial processes, such as the production of glass and pesticides. Ingestion of ARSENIC can cause serious health problems, including cancer, and long-term exposure can lead to organ damage.